This disclosure is concerned generally with flexible plastic bags used for collecting, processing and storing blood and blood components. The disclosure is especially concerned with a blood bag system found useful for separating, isolating and storing both old and young red cells on the basis of their relative densities.
The manufacture and use of flexible, plastic containers, or bags, for the collection, processing and storage of blood and blood components is well known. Whole blood from a donor is typically obtained via venipuncture and collected via tubing in a donor bag. The donor bag may or may not be connected via tubing to one or more satellite or transfer bags.
When connected to at least one transfer bag, the donor/transfer bag combination is commonly referred to as a "multiple" blood bag system. Such a system may include one, two, or three transfer bags, all in sealed communication with the donor bag so that, once blood or blood components are introduced into the system, the whole blood or its components may be moved from one bag to another by external manipulation of valves, and the like, thereby avoiding or minimizing contamination. Such multiple bag systems are thus commonly referred to as "closed" blood bag systems. Multiple blood bag systems not in sealed communication with the donor bag, or designed for attachment to the donor bag following initial collection are generally referred to as "open" blood bag systems.
In a typical multiple blood bag application, whole blood is collected into a donor bag and all connected transfer bags, which are typically empty, are placed in a centrifuge cup designed to hold the filled donor bag in a generally upright position. The bag contents are then centrifuged to separate whole blood into its lighter plasma component and its heavier red blood cell component.
By manipulating a valve, which typically is a frangible valve within the system, the upper plasma may then be expressed into one of the transfer bags, possibly for further processing (e.g., into platelet-rich and platelet-poor components which may be expressed further into other connected transfer bags). The separated platelet-poor plasma component subsequently may be fractionated into a variety of other products useful in so-called component therapy, including clotting factors, immune serum globulins, albumin, and the like.
During the first separation of plasma from red blood cells in a centrifuged donor bag, the upper plasma portion is often removed from the donor bag using a relatively simple device known as a plasma expresser. The expresser simply squeezes the donor bag until the upper, less dense plasma is fully expressed out of the bag, typically into a connected transfer bag.
In U.S. Pat. No. 4,857,190 (Wada et al.), a blood bag for separating white blood cells from platelets is shown. In that disclosure, a conventional blood bag is modified at the bottom to provide a small receptacle for collection and isolation of white blood cells (WBCs) from a platelet/WBC mixture. That disclosure focuses on minimizing the interface between the separated platelets and WBCs by carefully controlling the volume and dimensions of the continuous receptacle and by providing a centrifuge insert adapted to accommodate the bag and receptacle.
In U.S. Pat. No. 3,911,918 (Turner), there is disclosed an hour-glass shaped plastic blood bag comprising several compartments for the separation and isolation of blood components. That bag is capable of being separated to form a number of individual storage compartments for the separated components following component separation. As pointed out in that patent, prior art blood storage containers previously had not been detailed in size and shape to contain a predetermined quantity of blood or a blood component, such as plasma, in separate compartments.
More recently in U.S. Pat. No. 4,416,778 (Rogers), there is disclosed a dual compartment plastic blood bag in which the two compartments are connected via a tubing. The tubing includes a valve adapted to open only after a given centrifugation force is obtained. The bag is said to be especially useful for separating less dense and relatively younger red blood cells (i.e., neocytes) from more dense and relatively older red blood cells (i.e., gerocytes). As pointed out in that patent, the teachings of which are incorporated herein by reference, the use of neocytes is thought to be useful in minimizing iron overload possibilities in patients who depend on repeated blood transfusions.
To date, the primary method used for separating various blood components is simple centrifugation using either conventional bags or specially designed blood bags or using a specialized mechanical apparatus. One apparatus useful for separating blood components, including neocytes and gerocytes, is an instrument known as an IBM Model 2991 blood cell separator.
Unfortunately, the bags and apparatus available for fine separation of blood components tend to be fairly complex and expensive, thus limiting their use. Various ways of providing simpler, less costly methods and devices for the separation and isolation of blood components, especially the separation of neocytes and gerocytes, have been investigated recently.
An elongated bag specifically designed for neocyte preparation is described in U.S. Pat. No. 4,892,537 (Carmen et al.). See also continuation U.S. Pat. No. 4,969,882 to the same inventors. That system does not provide a way for saving gerocytes for later use. Furthermore, in that system the supernatant is expressed along with the neocytes into the satellite bag, which results in a generally undesirable increase in total neocyte transfusion volume.
In practicing that patented system, the tubing leading from the donor bag to the elongated bag is often severed after both transfer of the RBC mixture into the elongated bag and centrifugation. The supernatant is then expressed out of the severed tube, and the remaining packed neocytes are transferred into the satellite bag. The remaining gerocytes are viscous and generally are not used. Thus, it is desirable to provide a self-contained system for introducing a diluting solution into the main bag to enable storage and subsequent use of gerocytes from a neocyte/gerocyte mixture.